Fine Gael has accused Ireland's largest airlines of operating a cartel after Aer Lingus yesterday increased its baggage charges.
The charge by the party's transport spokesman Fergus O'Dowd coincides with a claim by the aviation regulator that Ryanair is attempting to intimidate his office.
Ryanair chief executive Michael O'Leary has clashed regularly with the head of the Commission for Aviation Regulation (CAR) Cathal Guiomard over enforcement of passenger rights legislation.
Ryanair has consistently criticised the CAR for failing to control airport charges and today re-iterated its call for his sacking.
Mr O'Leary and Mr Guiomard clashed on television last night after a consumer survey found Irish airlines were the most-complained-about in Europe with passengers complaints doubling over the past 12 months.
Mr Guiomard said Ryanair was a particularly difficult company to deal with and today he told RTÉ news that its lawyers were attempting to intimidate his staff.
"Ryanair have sent me ten letters from their chief lawyer. I deplore the tone of those letters, they are a naked attempt to intimidate this office and to discourage our staff from enforcing this legislation," he said.
Earlier this year, the airline introduced baggage-handling charges and yesterday Aer Lingus did likewise.
Mr O'Dowd said both airlines were using their power in the Irish market to "operate an effective cartel and impose unjustified stealth charges".
"Both airlines are increasingly using a business model which uses low fares to tempt customers, and then claws back revenue through additional charges," Mr O'Dowd said.
He said passengers should protest about the charges when checking in.
Ryanair has been accused of using a range of stealth charges to mask it prices while yesterday's increase by Aer Lingus was its third since it introduced baggage charges last January.
Baggage booked online went from €4 per item at the start of the year to €9 now. The cost for luggage registered at the airport went from €8 per bag to €12 over the same period.